Aerial system comprising a concentric transmission line



NOV. 4, 1952 J sTo 2,617,028

AERIAL SYSTEM COMPRISING A CONCENTRIC TRANSMISSION LINE Filed Feb. 15,1949 l/VVE/VT'OR Jon Stolk AGENT Patented Nov. 4, 1952 AERIAL SYSTEMCOMPRISING A CONCEN- TRIC TRANSMISSION LINE Jan Stolk, Eindhoven,Netherlands, assignor to Hartford National Bank and Trust Company,Hartford, Conn., as trustee Application February 15, 1949, Serial No.76,434

In the Netherlands April 16, 1948 of the interruption, in which eventthe envelopeof the transmission line is connected to one part of theinterrupted radiator and the inner conductor to the other part thereof,a troublesome current flows alon the outside of the envelope as a resultof the different capacities of the two parts of the interrupted radiatorwith respect to the envelope. As a rule, this current acts upon theradiation diagram in an undesirable manner.

It is known to interrupt such superficial currents by a sectionconnected in series with the outer surface of the envelope; However,this section exhibits properties which are dependent on frequency sothat the superficial current is completely suppressed for one frequencyonly. This is an inconvenience more particularly in the case of aerialshaving broad-band properties and with tunable aerials.

The present invention provides a construction in which the saidinconvenience is obviated.

The invention exhibits the characteristic that the inner conductor ofthe transmission line is connected to that extremity of one part of theinterrupted radiator which is adjacent the interior, the inner conductorbeing led in an insulated manner through the interior of the other partof the interrupted radiator as far as the external extremity thereof andthence led through the interior of a non-interrupted radiator andthrough an aperture provided midway of the last-mentioned radiator tothe exterior, extending from this point through a distance equal to atleast a quarter wavelength in a direction at right angles to thelongitudinal axis of the radiator, the envelope of the transmission linebeing connected to the centre of the last-mentioned radiator.

As will appear hereinafter, the aerial system is thus renderedsymmetrical with respect to the envelope, the symmetry obtained notbeing dependent on frequency.

It is noted that an aerial system connected to 5 Claims. (01. 250-33) 2a concentric transmission line exhibiting frequency-independent symmetryis known per se. However, such an aerialsystem is a frame aerial.

Furthermore it may be mentioned that a dipole, aerial is known in whichthe coupling with a concentric transmission line is established by meansof a coupling section which is somewhat similar to the'aerial systemaccording to the invention. However, in this known system, separatedipole radiators are secured to the coupling system.

The invention will now be explained more fully by reference to theaccompanying drawing, showing, by way of example, one form ofCOIlStlllCe tion of the system according thereto.

The aerial systemshown comprises three tubular radiators I, 2 and 3,each having a length of approximately V in which i represents thewavelength at the centre of the wavelength range thatmay b covered bythe aerial. The radiator 3 is interrupted midway at 4. At'the;extremities, the radiators l, 2 and 3 are interconnected by connectionsiand 6, which are like wise tubular. The spacing ofthe 'radiators'issmall with respect to A. The radiators here ex? tend in a plane, butthisis not essential. Here use is made of three radiators, but in aerialsystems according to the invention it is also possible to utilise two ormore than three radiators connected in parallel. A core 1 of atransmission line I, 8 is connected to the upper part of the radiator 3and, in the manner shown, led in an insulated manner through the lowerpart of the radiator 3, through the connecting piece 5 and through thelower half of the radiator l.

The last-mentioned radiator exhibits midway at 9 an aperture throughwhich the core 1 is led to the exterior. The envelope 8 of thetransmission line I, 8 is connected along the edge of the said apertureto the radiator I, the aerial system thus being geometrically symmetricwith respect to the envelope 8. Voltages set up in phase oppositionbetween the adjacent extremities of the interrupted radiator 3 now donot result in currents being produced along the outside of the envelope8.

It has been found that the symmetry is not disturbed to any appreciableextent if the transmission line 1, 8 is not exactly at right angles tothe longitudinal axes of the parallel radiators in so far that part ofthe transmission line is concerned which is farther than AA remote fromthe aerial system.

What I claim is:

1. A folded dipole aerial structure adapted to operate within apredetermined wavelength range comprising first and second parallelradiating elements of substantially equal length, the spacing betweensaid elements being less than a quarter of a wavelength of the centralwavelength in said range. first and second conductors having a lengthrelatively small with respect to said elements and interconnecting therespective extremities of said first and second elements, said secondelement being divided at the midpoint thereof to form a first sectionand a second section, said first section of said second element,

the corresponding portion of said first element.

and said first conductor being hollow, and a concentric line for feedingsaid radiators, said line having an outer conductor connected to themidpoint or said first element, and an inner conductor extending throughsaid hollow portion of said first element, said hollow first conductorandradiating elements having a length substantially equal to one halfthe wavelength of the central wavelength in said range, the spacingbetween saidxelements being. less. a q ar e f, a wavelength of saidcentral wavelength, first and second conductors interconnecting therespective extremities of said elements. Said; second element beingdivided at the midpoint thereof to term afirst section and a secondsection, and first sectionof said Second element, thecorrespondingportion of. said first element and said first condusterbeing hollow, and a concentric trans ission line ieed ns said elemen s.sa d line 1 an outer conductor connected to the mi p int at said. that eeme t n p s d a r ght angles thereto and having an inner conductorextending through the hollow portion of said first element, the hollowfirst conductor and the h0llow first section and being connected to thefree end of said second section.

4.'A foldeddipole aerial "system adapted to operate within apredetermined wavelength range comprising first and second parallelhollow radiating elements having a length substantially equal to onehalf the wavelength of the central frequency in said range, a thirdparallel radiating element of like length interposed between said firstand second elements, hollow first and second conductors interconnectingthe respective extremities of said first, second and third elements andcommunicating therewith, the

spacing between said elements being less than a quarter of a wavelengthof the central wavelength in said range, said second element beingdivided at the midpoint thereof to form a first sectio and a second s cion, and a con en r ansmission line for feedi g said el ment and avin atubu ar u e onduct r ccnnec ed to and communicat n th said firs el m ntat e m dpoi t t e eof a d an inne conduc or extend n t o g ne half o sar e ment and throu h aid. firs c ndu or and said, firs ect o o s d seond l en a d g; connected to the free end of said second section.

5. An arrangement, as set forth in claim 4, her in sa ute conduct r of,said. concentr line d sp sed at right. an e to sai first lement.

J AN TOLK,

' REFERENCES CITED v The following references are of record in the fileof this patent:

U TED STA ES ATE TS dcian ---,-i-s-.- Mer- 29 5:9-

